Objective: To investigate the clinical characteristics and antithrombotic treatment strategies in patients with acute ST-segment elevation myocardial infarction (STEMI) who develop new-onset atrial fibrillation during the acute phase and undergo emergency percutaneous coronary intervention (PCI), and to evaluate the association between new-onset atrial fibrillation and prognosis in STEMI patients. Methods: This retrospective cohort study consecutively enrolled 142 STEMI patients with atrial fibrillation who underwent coronary angiography and emergency PCI via the emergency green channel at the Department of Cardiology, General Hospital of Northern Theater Command from March 2016 to March 2022. Patients were divided into two groups based on the presence of new-onset atrial fibrillation: the prior atrial fibrillation group (n=61) and the new-onset atrial fibrillation group (n=81). Clinical baseline data, in-hospital and long-term antithrombotic strategies after discharge, and adverse events during follow-up were recorded and compared between the two groups. Multivariate Cox regression analysis was used to assess the association between new-onset atrial fibrillation and adverse outcomes. Results: The mean age of the 142 STEMI patients was (68.0±11.5) years, with 104 males accounting for 73.2%. New-onset atrial fibrillation accounted for 57.0% (81/142) of the patients. Compared with the prior atrial fibrillation group, patients in the new-onset atrial fibrillation group were younger, had a lower prevalence of diabetes and previous stroke, and had lower CHA2DS2-VASc and HAS-BLED scores. Additionally, a higher proportion of patients in the new-onset atrial fibrillation group presented with Killip class Ⅳ at admission. During hospitalization, the new-onset atrial fibrillation group had a higher proportion of amiodarone use and lower prescription rates of angiotensin-converting enzyme inhibitors or angiotensin Ⅱ receptor blockers. Regarding long-term antithrombotic strategies after discharge, patients in the new-onset atrial fibrillation group more frequently received dual antiplatelet therapy (67 (82.7%) vs. 37 (60.7%)), while those in the prior atrial fibrillation group more often received anticoagulation combined with dual antiplatelet therapy (20 (32.8%) vs. 8 (9.9%), P<0.05). During 12-month follow-up, the incidence of net adverse clinical events was 18.5% (15/81) in the new-onset atrial fibrillation group and 24.6% (15/61) in the prior atrial fibrillation group, with no significant difference between the two groups (P>0.05). Multivariate Cox regression analysis confirmed that new-onset atrial fibrillation was not independently associated with adverse outcomes (HR=0.73, 95%CI: 0.31-1.69, P=0.459). Conclusions: More than half of the STEMI patients with atrial fibrillation undergoing emergency PCI had new-onset atrial fibrillation, characterized by a lower prevalence of diabetes and stroke, as well as a greater likelihood of receiving dual antiplatelet therapy as the long-term post-discharge antithrombotic strategy. However, new-onset atrial fibrillation was not independently associated with adverse outcomes. 目的： 探讨接受急诊冠状动脉介入治疗的急性ST段抬高型心肌梗死（STEMI）急性期新发心房颤动（房颤）患者的临床特征、抗栓治疗策略，以及新发房颤与STEMI患者预后的相关性。 方法： 本研究为回顾性队列研究，连续纳入2016年3月至2022年3月于解放军北部战区总医院心血管内科经急诊绿色通道行冠状动脉造影及急诊经皮冠状动脉介入治疗，同时合并心房颤动的142例STEMI患者为研究对象，根据是否为新发房颤，分为既往房颤组（n=61）与新发房颤组（n=81）。记录并比较两组患者的临床基线资料、院内和出院后长期抗栓策略以及随访期间不良事件发生情况，并通过多因素Cox回归分析新发房颤与不良预后的相关性。 结果： 142例STEMI患者年龄（68.0±11.5）岁，男性104例（73.2%），新发房颤57.0%（81/142）。与既往房颤组相比，新发房颤组年龄较小，合并糖尿病、既往卒中比例较低，同时CHA2DS2-VASc评分及HAS-BLED评分均较低，入院后Killip Ⅳ级比例较高；新发房颤组患者住院期间胺碘酮使用比例较高、血管紧张素转换酶抑制剂或血管紧张素Ⅱ受体拮抗剂药物的使用率较低。对于出院后长期抗栓策略选择，新发房颤组更多采用双联抗血小板治疗［67（82.7%）比37（60.7%）］，而既往房颤组更多选择抗凝联合双联抗血小板治疗［20例（32.8%）比8例（9.9%）］，差异有统计学意义（P<0.05）。随访12个月，净不良临床事件发生率新发房颤组为18.5%（15/81），既往房颤组为24.6%（15/61），差异无统计学意义（P>0.05）。多因素Cox回归分析显示新发房颤与STEMI患者不良预后无相关性（HR=0.73，95%CI：0.31~1.69，P=0.459）。 结论： 接受急诊PCI治疗的STEMI急性期房颤患者中超过半数为新发房颤，其合并糖尿病、卒中的比例较低，出院后长期抗栓策略更多采用双联抗血小板治疗，新发房颤与不良预后无相关性。.